The invention is directed to clamping devices for use in holding a straight edge in a predetermined position while using such straight edge as a guide for drawing a straight line, cutting glass, sawing, cutting mats for pictures, and any other uses for which a straight edge is required. In using a straight edge, there are a number of features which would be desirable if attainable. For example, of primary importance in assuring that the job does not have to be repeated due to slippage of the straight edge, it is desirable to provide means to maintain the straight edge in place during operation. Preferably, such means will be easy to use and allow proper alignment of the straight edge in as expedient a manner as possible. Heretofore, it was common practice to use a hand and the weight of the body to hold a straight edge in place. However, such a practice does not assure that the straight edge will stay in position during use. In addition, such use of the straight edge involves a strain upon the individual to the extent that it is necessary to exert a positive force upon the straight edge while drawing a line, cutting, etc. In those instances involving larger workpieces in particular, there is also the problem of the awkward positioning of the body and the discomfort resulting therefrom.
Efforts have been made to overcome such problems. For example, it has been suggested that a nail be positioned at both ends of the straight edge to hold it in place. This is obviously a time consuming process and requires putting holes into the board or other surface upon which the workpiece is positioned.
Others have suggested the use of a hand clamp similar in construction to spring biased pliers. Or, alternatively, to a C-clamp. Such devices have limited application in that if pressure is exerted against the straight edge during the drawing or cutting operation, the straight edge will have a tendency to swing out of alignment.
Prior attempts to design a holder have included the use of a device having a pressure-applying member of elliptical cross section which is rotatable relative to a frame and which, when pivoted within such frame, frictionally grips the board and straight edge between such member and a guide. Such device provides limited contact between the pressure-applying member and the straight edge to the extent that such contact is solely along a line defining the high point of the elliptical surface. Accordingly, it can be expected that the degree of pressure distribution is limited and that pressure exerted against the straight edge may cause it to move. In addition, in such a device, the elliptical surface directly engages and, therefore, may undesirably deface the surface of the straight edge, particularly when such straight edge is a wooden or plastic T-square. A prior art device of this type also includes an L-shaped guide which is moved vertically to meet the bottom of the drawing or cutting board, and for this purpose is provided with two screws which must be tightened to hold the guide in place. Such screws ride in slots, and to assure proper contact with the cutting or drawing board requires that the screws be moved to a uniform degree along the slots. Otherwise an imbalance may occur having an adverse affect upon the maintaining of the straight edge in place. In addition, in such a device the structural relationship between the straight edge and its associated holder has restricted the orientation of the straight edge such that it is substantially perpendicular to the edge of the drawing or cutting board and cannot be angularly oriented if desired.
Many other prior art devices exist but such devices appear to include either complex mechanisms or clamping structure not adequate to maintain the straight edge in position in those instances requiring pressure upon the straight edge.
Accordingly, it is an object of this invention to provide a clamping device which maintains a straight edge in place while pressure is being exerted thereupon.
Another object of this invention is to provide a clamping device which may be locked in position with minimum effort.
Still another object of this invention is to provide a clamping device which allows for proper alignment of a straight edge in an expedient manner.
A further object of this invention is to provide a clamping device the use of which involves a minimum amount of strain upon, and awkward positioning of, the body of the user of such device.
Still a further object of this invention is to provide a clamping device the use of which allows for maintaining a straight edge in place without defacing the underlying board or straight edge.
Yet another object of this invention is to provide a clamping device which prevents a straight edge from swinging out of alignment when pressure is exerted thereupon.
Another object of this invention is to provide a clamping device which adequately distributes the pressure upon a straight edge to hold it in place.
Still another object of this invention is to provide a clamping device having means to accurately adjust such device for use with boards of various thicknesses.
Yet another object of this invention is to provide a clamping device which does not comprise a complex mechanism.
Another object of this invention is to provide a clamping device which allows for orienting the straight edge at any desired angle relative to the edge of the board.